可以通過(guò)以下兩種方式轉(zhuǎn)換，原理都是一樣的，只是使用方式不一樣。

給 String 添加擴(kuò)展

extension String {
    func uicolor(alpha: CGFloat = 1.0) -> UIColor {
        // 存儲(chǔ)轉(zhuǎn)換后的數(shù)值
        var red: UInt32 = 0, green: UInt32 = 0, blue: UInt32 = 0
        var hex = self
        // 如果傳入的十六進(jìn)制顏色有前綴，去掉前綴
        if hex.hasPrefix("0x") || hex.hasPrefix("0X") {
            hex = hex.substring(from: hex.index(hex.startIndex, offsetBy: 2))
        } else if hex.hasPrefix("#") {
            hex = hex.substring(from: hex.index(hex.startIndex, offsetBy: 1))
        }
        // 如果傳入的字符數(shù)量不足6位按照后邊都為0處理，當(dāng)然你也可以進(jìn)行其它操作
        if characters.count < 6 {
            for _ in 0..<6-characters.count {
                hex += "0"
            }
        }
        
        // 分別進(jìn)行轉(zhuǎn)換
        // 紅
        Scanner(string: hex.substring(to: hex.index(hex.startIndex, offsetBy: 2))).scanHexInt32(&red)
        // 綠
        Scanner(string: hex.substring(with: hex.index(hex.startIndex, offsetBy: 2)..<hex.index(hex.startIndex, offsetBy: 4))).scanHexInt32(&green)
        // 藍(lán)
        Scanner(string: hex.substring(from: hex.index(startIndex, offsetBy: 4))).scanHexInt32(&blue)
        
        return UIColor(red: CGFloat(red)/255.0, green: CGFloat(green)/255.0, blue: CGFloat(blue)/255.0, alpha: alpha)
    }
}

調(diào)用

"FF0000".uicolor() // red

給 UIColor 添加擴(kuò)展(實(shí)際代碼還是那些)

extension UIColor {

    /// 用十六進(jìn)制顏色創(chuàng)建UIColor
    ///
    /// - Parameter hexColor: 十六進(jìn)制顏色
    /// - Parameter hexColor: 透明度
    convenience init(hexColor: String, alpha: CGFloat = 1.0) {

        // 存儲(chǔ)轉(zhuǎn)換后的數(shù)值
        var red: UInt32 = 0, green: UInt32 = 0, blue: UInt32 = 0
        var hex = self
        // 如果傳入的十六進(jìn)制顏色有前綴，去掉前綴
        if hex.hasPrefix("0x") || hex.hasPrefix("0X") {
            hex = hex.substring(from: hex.index(hex.startIndex, offsetBy: 2))
        } else if hex.hasPrefix("#") {
            hex = hex.substring(from: hex.index(hex.startIndex, offsetBy: 1))
        }
        // 如果傳入的字符數(shù)量不足6位按照后邊都為0處理，當(dāng)然你也可以進(jìn)行其它操作
        if characters.count < 6 {
            for _ in 0..<6-characters.count {
                hex += "0"
            }
        }
        
        // 分別進(jìn)行轉(zhuǎn)換
        // 紅
        Scanner(string: hex.substring(to: hex.index(hex.startIndex, offsetBy: 2))).scanHexInt32(&red)
        // 綠
        Scanner(string: hex.substring(with: hex.index(hex.startIndex, offsetBy: 2)..<hex.index(hex.startIndex, offsetBy: 4))).scanHexInt32(&green)
        // 藍(lán)
        Scanner(string: hex.substring(from: hex.index(startIndex, offsetBy: 4))).scanHexInt32(&blue)

        self.init(red: CGFloat(red)/255.0, green: CGFloat(green)/255.0, blue: CGFloat(blue)/255.0, alpha: alpha)
    }
}

調(diào)用

UIColor(hexColor: "FF0000") // red